The present invention relates to a semiconductor integrated circuit design system, a semiconductor integrated circuit design method, and a computer readable medium.
In designing a semiconductor integrated circuit, cells are designed by creating a circuit pattern with use of a minimum possible design rule in a miniaturization technique, and then these cells are placed and routed to make an entire LSI chip design. Subsequently, this layout design pattern is subjected to layout check and correction by LVS (Layout Versus Schematics), DRC (Design Rule Check) and the like. Subsequently, optical correction and pattern adjustment are conducted in processing steps including OPC (Optical Proximity Correction) and MDP (Mask Data Preparation), and the like. Thereafter, the process proceeds to a lithography checking step and then to a wafer fabrication step.
In this way, it has been a conventional practice to make correction and adjustment to imperfections and the like in each process step while fabricating a silicon wafer from a layout pattern of a semiconductor integrated circuit.
However, because a dimension of each transistor or each wire formed on a semiconductor wafer has been reduced to a value substantially equal to a wavelength range of light, it has become difficult to process silicon according to an intended design pattern in the fabrication process. This is because, due to miniaturization and growing integration of mask patterns, neighboring pattern placements have an influence on each other during formation of the pattern by lithography or etching.
In recent years, it has been a common practice to conduct OPC in which a correction pattern is previously added to a design pattern so that desired dimensions are obtained after processing. However, it takes very much processing time for achieving a highly integrated layout pattern with precision. In some cases, proper pattern correction processing cannot be achieved, with the result that the electrical characteristics of a device vary beyond prescribed ranges, thus lowering the chip fabrication yield.
In an attempt to overcome such a problem that a design pattern is generated which cannot be adequately corrected by the OPC processing, a proposal has been made of a method including detecting a pattern that cannot be properly corrected by OPC and correcting a design rule while fabricating a mask pattern.
However, if such a pattern that cannot be properly processed by OPC is merely inhibited, it is still difficult to remove a false error which is not problematic in designing to progress the design. Thus, a problem exists that a great deal of time and labor is required in optimization of the OPC recipe and correction of the design rule for redesign.
A design pattern that is difficult to process by lithography not only exercises a serious effect on fluctuations of electrical characteristics due to a finely processed device structure as well as on the performance and reliability of a semiconductor integrated circuit but also may cause a short circuit or a disconnection in wiring to occur with a certain probability, thus deteriorating the yield. Therefore, when a design pattern that cannot be properly processed by OPC is generated, the process has to be returned from the pattern processing step to the layout design step in order to correct the design pattern itself.
A conventional process from layout design to mask fabrication allows numerous errors to occur at an LRC (Lithography Rule Check) step. Among these errors, a number of false errors are included which are not problematic in designing. The number of true error parts of a layout that necessarily call for pattern corrections is relatively small. However, it takes a great deal of time to judge the numerous errors including such false errors. Thus, the conventional design method involves a problem that a long design period and an increased design cost are required.